Brake linkage



Sept. 19, 1933. E. R. EVANS 1,927,632

BRAKE LINKAGE Fileu. Jan. 29, 1932 4 Sheets-Sheet 1 9 A q Q l C I L U 1 g I.

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BRAKE LINKAGE Filed Jan. 29, 1932 4 Sheets-Sheet 2 Edwin/3.50mi? 1 WWW Filed Jan. 29, 1932 4 Sheets-Sheet 3 v Q [warlor- 14v 0212. [0am W-=-% Sept. 19, E. R EVANS BRAKE LINKAGE Filed Jan. 29; 1932 4 Shets-Sheet 4 Eda/U2 E. i i/(Z726,

Patented Sept. 19, 1933 I mom was BRAKE I e Edwin n; Evans, omega, n1.

I Amimm M ri za 1932.; sensin /589,589 3 Claims. "(01. 188-40 The present invention relates to improvements in the brake linkage of motor vehicles particularly vehicles having four-wheel brakes.' v l It has previously. been proposed to use wheel brakes for motor vehicles including a pair of brake in opposite directions, one shoe of each brake will be a wrap shoe and theother an unwrap shoe, depending upon the direction in which the vehicle is traveling. The wrap shoes in such a system will develop a greater amount of breaking pressure than the unwrap shoes. i v It is an object of the present invention to transmit a greater brake applying force to the unwrap shoes of the wheel brakes during forward travel of the vehicle than to the wrap shoes,

whereby the effective braking of the be substantially equalized.

It is further an object of the present invention to transmit greater pressure to the unwrap 'brake shoes by transmittinga brake applying 3 force to rock shafts which areuniversally supported-on the axles of the vehicle in such manner as to produce not only rotation of the rock shafts but also a leverage which tends' to rotate each of the rock'shafts angularlyabout its support upon the axle in such a manner-that, the brake applying earns are'moved towards the unwrap brake shoes. L i 7 Further objects and advantages of the present following description taken in connection with r the attached drawings, in which f Figure 1 is a iplanview of the brake linkage; Figure 2 is a side elevation of the'brake linkage; Figure 3 is an elevation of the rock shafts sup-1 ported upon the frontaxle; V Figure 4 is a plan view of the rock shafts sup ported upon thefront axle; v

Figure 5 is a plan view of the rock shafts sup-v ported upon the rear axles; o Figure 6 is an elevation of the rock ported upon the rear axles;

Figure '7 is a detail section taken on'the plane indicated 77 in Figure 6; 7

Figure 8 is :an elevation similar to Figure 3 shafts supures 8 an .l

' wheel brake is. called a normallyenergized brake shoes will invention will -be more readily apparent frorn the showing afrnodified support :for the rock shafts .uponjthe front axle; i

Figure 9 is a plan view of the rock shafts shown inFigure8,and Figure 10 'isa detail transverse 'sectionillus trating'the, support for the rock shafts shown The chassis frame and general arrangement of the brake linkage --isiillustrate d in Figures 1 r and 2. There is shown 'a frontiaxle. '10, a .pair of front wheel brakes 12 -12;a3rear: axle 'f14; "and a pair off rear, wheel brakes l6.-.16. The front wheel brakeconstructionis shown to ='comprise .a

pair of segmental brakeshoes 18%1 8whichbear p at their upper spaced ends. against-an adjustable anchor pin 20 and bear at their lower-spaced ends '1 against a rotatable brake actuating cam 22.,The:

brake shoes are normally held in released fposi-i' tionby thegrelease springs 24. This type of since, upon f actuation; one; of thei shoesywillihave a tendency to;-wraptowards the anchor *pinrdue to therotatlon ofthe brake drurn;andthe other shoe will havea tendency tounwr'apjaway from the anchor pin..-;Therefore, under normal-con dition of operati'omone shoe would be anener gized shoeand would. develop greater braking pressure than the othershoe.v Thus; during forward travel of the vehicle the rearward shoe of thepair of'brakeshoes 18.-18woul'd be the shoe having a tendency to. wrap towards'gthe anchor pin and thereby developing greaterbrakingpresa sure than'the forward'shoe.

It is a feature ofathepres'ent inventionthat the brake'linkagelis 'so designed that the brake V applyingxforce not only tends to rotate "the can to. expand'the fbrake' shoes but also tends jto niove the cam'laterally in a direction to increa'se the bralfing pressure of the unwrapped shoejand thereby tendto equalizethe braking" pressures of the two shoes. The same action is' -brQught about infthe .rearwheelbrakes, one of which is shown in detail in Figure 2 and comprises a" ,pair of segmentabbrake shoes;-'26 26 bearing I at their rearward spaced ends against-an adjustable anchor pin'28 and bearing at their" f o 1 ward spaced ends against an expan'dingcam 30.

The shoes 26 'are held the springs-32.

30 1are'shown to be in ahorizontal planepass ins-released position" by .In the rear wheel brakes the -rotatable cams ing through the axis o'frotation 01' the wheels whereas the front wheel brake earns 22 are arranged in a vertical plane passing through the no axisof-r-otation ofthewheels. *Inthe rear wheel brakes during forward travel of the vehicle the upper shoes will have a tendency to unwrap away from the anchor pin and the lower shoes.

will have a tendency to wrap toward the anchor pin. Therefore to develop greater pressure upon the unwrap shoes of the rear wheel brakes, it. is" necessary to develop a'force upon the cam to produce not only rotation butalso upward movement of the cam.-

Figures: 1 an'df'2 "illustrate the :brakev linkage comprising a front cam actuating shaft 34 carrightrhand wheel brake.

riedby the front axle and connected to the ;cam 22 of the lefthand front wheel brake while .a second cam actuatingshaft-36 is'carriedby,

the axle10 and connected to the cam 22 of the The rear "axle";14 'siin ilarly supports a left-hand cam shaft 38 and a right-hand cam shaft 40. Thedetails' relat ing tothe formation of the cam shaftsanditheirii supports upon the axles will be later morefully described, but' it wi11-- be understoodlfrom*Fig-" ures 1' andZ that a pull rod 42 is'connected by pin 44totransmit actuating movement tothe transmits "actuating movement to the rear cam shaftsj38 and40. The' p'ullro'ds .42 and 46 are pivotally connected to the lower and upper arms of the bearing supports; I

front cam shafts 34 and, 36, while' 'a pull'r'od 46 respectively of a' double arm brake lever 48 which is carried by a rock shaft 50. V

f In theepresent disclosure I have shown the rock shaft -50 to bepart' of-a power brakef52 having an input rock shaft 54 adapted tobe controlled by input lever 56, pull rod 58 and 'pedal 60, which is ."carried by pivot 62. The powerfbrake 52 is 3 associated with the propeller shaft 64 and oper ates ina well-known manner to amplify lthe input force. producedby the actuation of the pedal and to transmit 'theamplified braking force through arotation'of the output rock" shaft 50 for actuation of the front and rear brakes Q The detail construction for the support of the front .Zcam'shafts, is shown in elevation-in Fig ure' 3 and in. planin Figure4; The'front axle 10 hassecured thereto a pair of bearing supports 66 and 68. each. of which is threaded into the swiveling axes 76 of 'the front wheels and there-.

. put leverage tending to produce rotation eithefore turning of the front wheels does notinterfere with the actuationof the brakes The ad jacent ends or the cam'shafts 34 and 36' are -vturned upwardly, as indicatedat 78 and';80, -so' that the axis of the pin 44, which is connected betweenthe upturned ends 78 and80 of the 'cam shaft to the end of the pull rod 42, is ofiset'wi'th respect to the normal axisjof rotation of the cam shafts. The amount of offset determines theinbrake camswhile the contour of thecams will determine the output leverage for producing expansion of the shoes upon rotation .of. the cams.

In addition,.how ever, the pull, of the rod 112-tends to rotate each. of the camshafts about the, vertical axes passing through thecenters; of the bearing supports 66- and 68., Therefore in Figure 4,--the end- .78-of;thejcan1jshaft34 will be movedjrearwardly and the cam 22on theouter end of the cam shaft will be moved forwardly tending to subject a greater pressure upon the unwrap brake shoe. The same action willoccur s x upon the 'otherrcain shaft 36. t will be noted that the pull rods 42 and 46 cannot, inpractice, be placed at the center of the vehicle and therefore the cam. shafts 34 and 36"cannot be of equal, length, but it is only necessary to so position the supportingbearings 66 and 68 such, that theyi'divide the shafts34 and'36 proportionately to obtain equalized braking pressures;

. Figures 5 and 6 illustrate in detail the rear wheel brake arrangement. The rear axle 14 carries supporting members 32'and 84. A pair of rear brake actuating crossshafts86 and 88, having spherical bearing members 90'and 92 are carried, with freedom for universal movement,

'by the s'uppor'ts'82 and 84 in the'same manner asthe front brake actuating cross shafts34 and 36. Adjacent one side of the diiferential housing 94 is; a yoke-shaped supporting member ,96

carried by. the axle .14; The support 9.6 carries a bell crank; lever 98 on pivot 'pinjlull. .The pull rod 45; ispivotally connected at;-102.; t0 the.

depending arm: of the bell, cranklev'er 98, while the adjacent ends-104 and 106. of the shafts are pivotally supported by the upper armof the bell crank lever93 through means ofa pivot pin 1 08.

RefeI'r'ing-to Figure '7 it will be apparent that actuation of-the pull rod 46 will rotate thebell crank lever -98- ina direction to-rotate the shafts 86 and 88 and also tend to move the ends 104 and 1060fv the-shaftsdownwardly whilethecams 3i) at the outer ends of the-shafts'will be moved up wardly thereby throwing greate1 ..pr e r upon theunwrap brake shoes.

actuating cams, 11;0 are at the. upper sides of the brakes, therefore, the reverse of theform'shown Figures 8,1,9 and 10 illustrate an arrangement which may be employed when the frontbrake in Figure 2. Inthis arrangement'a pair of brake actuating cross shafts 112 and-114 are u iversally supported at,116,,and118 upon'su'pportingmembers 120 and 122. In order to produce the proper movement of the shafts112 and 114, it isnecessary to employ a reversing arrangementsimi-lar to that disclosed in Figures .5, 6 and '7. .I therefore show 'a yoke-shaped support 124 carried: by

the axle 126 which pivotally supports at 128 a' bell cranklever 130 Whichlisjpivotally connected at its lower end 132 to theppull rod l34; ;The

upper end 1360f thebell crank lever is pivotallyl connected to the. bent ,end s 138 and 140 of thearock shafts 112- 114. Actuation of the pu1l-rod134 will rotate the .bell. crank lever .130. in a direction to rotate thecams. 110'and to move the cams, in rearward directions with respect to the motor vehicle, thereby throwing greaterpressure upon the'unwrap brake shoes.

h .It. will beunderstood thatsince the'cross carried by the axle may be actuated either'di rectly, as'in Figure '3, or through a reversing bell crank lever asiri Figures 5 and'8, itis possible-if so desired, to throw greater pressure upon the I wrapped shoes during forward jtravelof the vehiole. h V a I'claim: f j V 1. In a brake mechanism, an axle, wheel brakes carried by the endsof said-axle, each of said wheel brakes including a pair-of b'rake shoes, an,

anchor for said shoes adaptedto receive brake reaction from one of said shoes, a cam forexpanding both of said shoes and adaptedto .receive the brake reaction from the other,v of said shoes,j'a' pair ofrock-shafts; each of which is an unwrap shoe during application of the brakes,

brakes including a pair of brake shoes, one of which is a wrap shoe and the other ,of which is brake shoe expanding cams associated with said wheel brakes, a pair of rock shafts universally supported between their ends upon said axle, said shafts being connected at their outer ends to said cams, the inner ends of said shafts being offset from the normal axis of rotation of theshafts, a connection between the opposite inner ends of said shafts and means for transmitting a brake actuating force to said connection in sucha manner as to rotate the cams and to develop a material leverage action for moving the cams towards the unwrap brake shoes in at least one direction of travel of the vehicle.

3. In a brake linkage for motor vehicles, a front I axle, wheel brakes carried by the ends of said front axle, a rear axle, wheel brakes carried by the ends of said rear axle, each of said wheel brakes includingtwo shoes, .one of which is a: wrap shoe andthe other of which is an'unwrap shoe upon application of the wheel brakes during travel of the vehiclein one direction, a brake r expanding cam for each of said wheel brakes, a

to the cams'for the front wheel brakes anduniversally supported between their ends upon the front axle, a connection between the inner ends of said shafts, a pair of rock shafts connected at their outer ends to the cams of the rear wheel brakes and universally supported between their ends upon said rear axle, a connection between the inner ends of said last-mentioned rockshafts,

a doublearm brake lever positioned at an intermediate point on the vehicle and tension trans mitting means for connecting said brake applying lever to the front and rear brake actuating rock shafts at points intermediate the universal supports therefor whereby the cams are rotated for applying the wheel brakes and are moved towards the unwrap brake shoes in at least one EDWlZN R. EVANS.

, pair of rock shafts connected at'their outer ends 100 direction of vehicle travel. 

